android canvas 局部透明,Android Canvas清晰透明

rperryng..

12

解决方案是创建一个辅助画布和位图来绘制.我的自定义视图的onSizeChanged()方法看起来像

@Override

protected void onSizeChanged(int w, int h, int oldw, int oldh) {

super.onSizeChanged(w, h, oldw, oldh);

bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);

bitmap.eraseColor(Color.TRANSPARENT);

temp = new Canvas(bitmap);

}

和onDrawMethod看起来像

@Override

protected void onDraw(Canvas canvas) {

super.onDraw(canvas);

temp.drawColor(Color.argb(80, 0, 0, 0));

temp.drawCircle(centerPosX, centerPosY, 200, transparentPaint);

canvas.drawBitmap(bitmap, 0, 0, null);

}

其中transparentPaint在onstructor中声明为

transparentPaint = new Paint();

transparentPaint.setColor(getResources().getColor(android.R.color.transparent));

transparentPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));

transparentPaint.setAntiAlias(true);